Lukas Podolski inspired FC Köln to a 4-1 win over Bayer Leverkusen in Stale Solbakken and Robin Dutt's first Rhineland derby in charge of the respective local rivals.
Podolski created Cologne's first goal for Milivoje Novakovic just before half time before scoring the second just after the interval.
Podolski's second and Cologne's third sealed the win in the 54th minute before Simon Rolfes grabbed a consolation for the home side.
Andre Schurrle was sent off late on before Mato Jajalo completed the scoring with Cologne's fourth deep in stoppage time.
Borussia Monchengladbach climbed to second in the standings with a narrow 1-0 victory at rock-bottom Hamburg.
Igor de Camargo headed home the game's only goal in the 66th minute to send Lucien Favre's side level on 13 points with Werder Bremen at the summit, although Bayern Munich can regain top spot on Sunday with victory at Schalke.
The result was a fourth win in six games this term for Monchengladbach, who only avoided relegation last season courtesy of their play-off victory over Bochum, while for HSV it was a fifth defeat.
Nurnberg fought back to secure a hard-fought 1-1 draw in horrendous conditions against 10-man Werder Bremen.
Heavy rain made playing conditions almost impossible and the visitors were hardly helped by the early dismissal of goalkeeper Tim Wiese.
Mehmet Ekici put Werder ahead against the run of play but Philipp Wollscheid earned his side a deserved point with his second-half goal.
Hoffenheim kept up the pressure on the leaders as two goals from Roberto Firmino guided them to a 3-1 victory over Wolfsburg.
Former Liverpool forward Ryan Babel opened the scoring after 20 minutes before Brazilian Firmino doubled the lead three minutes later.
Ashkan Dejagah pulled one back before Firmino struck again four minutes from time, after Wolfsburg goalkeeper Marvin Hitz was sent off for abusive language.
Augsburg survived the late dismissal of Sebastien Langkamp to hold on for an decent 2-2 draw on the road at Hertha Berlin.
Hajime Hosogai fired the visitors into the lead in the first half but goals from Christian Lell and Tunay Torun early in the second period put Hertha in the driving seat.
Jan-Ingwer Callsen-Bracker's strike on 64 minutes secured a point for the promoted side, although they endured a nervy final few minutes after Langkamp saw red for a professional foul on Raffael.
Martin Harnik scored twice as Stuttgart gained a 2-1 victory at Freiburg.
The Austria forward netted in each half to put the visitors firmly in control, Papiss Cisse's 85th-minute effort coming too late for the hosts.
The win moved Stuttgart to within two points of Bayern Munich and Werder Bremen at the top of the table, although both teams have a game in hand.
